This invention relates to low-latency methods for transmitting data at a data processing system.
It is generally desirable to minimise the latency associated with sending messages over a network between applications. This enables a receiving application to receive a message the minimum possible time after the sending application forms the message.
It is especially important to minimise the latency over networks that connect high performance computing devices, or computing devices that must react as quickly as possible to incoming data in order to gain a commercial advantage, such as electronic trading devices. In electronic markets, messages sent over networks are used to submit orders and quotes to exchanges and it is often of considerable benefit for a computing system to be able to respond to external stimuli and submit orders and quotes ahead of competitors.
Applications running at computing devices on a network typically communicate over the network using an application-level protocol (such as HTTP or the Financial Information Exchange or FIX protocol) that define a series of structured messages. In order to form each message, the data for transmission must be processed in accordance with the application-level protocol (as well as lower layer protocols, such as Ethernet) in order to form a completed message that is ready for transmission over the network. Typically this protocol processing takes the form of generating headers and calculating error checks (such as CRCs). Such protocol processing can introduce significant latency into the transmission of data since in conventional data transmission systems a network protocol stack must wait for all of the data that is to form a message to be available before commencing protocol processing. This can significantly extend the time elapsed between an application determining that a message is to be sent and that message actually being transmitted onto the wire.
Other causes of transmission latency in conventional systems include the restriction for connection-oriented protocols (such as TCP) that only the protocol stack that negotiated the connection can transmit over the connection. Often such a protocol stack is supported at a host kernel, which does not present a low latency transmission path to applications of the system. Additionally, a modern processor can introduce significant latency if the state and instructions required by a transmission process is not available in cache at the processor.
There is therefore a need for improved methods for transmitting data at a data processing system that reduce the latency associated with message transmission.